"We've had two very different presidents pretty much doing the same thing with regard to electronic surveillance. That seems to me to suggest that these things do work," Hayden said on Fox News Sunday.

The administration has sought to fend off criticism of the program which combed through the phone and Internet records of millions of Americans, saying it was needed for national security reasons. On Saturday, the National Security Agency filed a report requesting a criminal investigation to find who leaked details of the surveillance activities to the Guardian and The Washington Post.

Hayden served as head of the NSA from 1999 to 2005, and explained that the records are not used to search indiscriminately. He gave an example of a cell phone being found in Waziristan -- a mountainous region in the northwest of Pakistan -- then the number being plugged into the records to see which other phones had made or received calls from the phone.

He admitted that all other records are kept, but are never looked at unless they are linked to terrorism.

"If you don't have any link to that original predicate, terrorism, your phone records are never touched," Hayden said.

The disclosure of the surveillance program has set off a political firestorm in Washington, with libertarian-leaning Republicans joining liberal Democrats in condemning the program, while national security advocates in both parties supported the monitoring of phone calls.

But Republican Rand Paul of Kentucky said on Fox News that Americans should join a class-action lawsuit to force the issue to the Supreme Court.

After the recent hearings on the IRS targeting groups because they had conservative sounding names, many Americans feel the NSA's data mining could lead to similar abuse of political enemies.

But Hayden said there are no records of abuse of the system under President George W. Bush, under whom he served, or under President Barack Obama.

"I was criticized because I theoretically didn't have enough oversight mechanisms," Hayden said. "But no one accused us of abuse."

As a senator, Obama voted against Hayden's nomination to head the CIA because of his NSA background. But as president, Obama has expanded the surveillance program, adding to the volume to what is collected, Hayden said. Obama also added oversight mechanisms and put the program under congressional authorization rather than under the president.

"NSA is actually empowered to do more things than I was empowered to do under President Bush's special authorization," he said, adding that there has been "incredible continuity between the two presidents."

The former head of the National Security Agency defended on Sunday the government's program of saving metadata of all telephone calls for future searches. Gen. Michael Hayden, former head of the NSA and CIA, said the programs that have come under scrutiny in the past week...